Bring water to a boil in a large pot. Salt the water and add in macaroni. Stir and cook until al dente, about 8 to 10 minutes. Drain and set aside.
Make the avocado sauce by placing the garlic, avocados, lime juice, cilantro, salt and pepper into a food processor or blender. Process until smooth and creamy. Set aside.
To make the cheese sauce, place butter in a small saucepan and heat over medium heat. When butter is melted, whisk in flour to create a paste. Whisk in milk until smooth. Stir with a wooden spoon until the sauce starts to thicken Add in pepper jack cheese and stir until cheese is melted and sauce is creamy.
Place macaroni in a large bowl. Pour the avocado sauce over the macaroni and stir until well coated. Add the cheese sauce and stir until macaroni is coated and creamy. Season with salt and pepper, to taste. Serve warm.
Garnish with fresh avocado chunks, if desired.

(This recipe was contributed as part of a "Cook of the Week" feature.)